Nozzle apparatus in a spray coating station and a method for changing the mouthpiece

ABSTRACT

The present invention relates to a nozzle device for use in a spray coating station designed for coating a paper or board web, said device comprising a nozzle device body ( 1 ), a replaceable nozzle piece ( 2 ) and clamping member and actuator ( 3,4 ) suited to lock said nozzle piece ( 2 ) to said nozzle device body ( 1 ). New nozzle pieces ( 2 ) are stored in a nozzle replacement apparatus ( 5,6 ) which facilitates rapid replacement of an in-use nozzle piece ( 2 ). In the replacement operation, the clamping member and actuator ( 3,4 ) serving to lock said nozzle piece ( 2 ) are first actuated in order to release said nozzle piece whereafter the worn nozzle piece ( 2 ) is removed with the help of transfer member ( 6 ) and a new nozzle piece ( 2 ) is moved to the nozzle device, and finally said new nozzle piece ( 2 ) is locked by said clamping member and actuator ( 3,4 ) to said nozzle device body ( 1 ).

FIELD OF THE INVENTION

The present invention relates to a nozzle device comprising at least anozzle device body with a nozzle orifice located therein. Such nozzledevices are used in spray coating stations designed for coating a paperor board web, whereby a single coating station may include up tohundreds of nozzles.

The invention also concerns a method for replacing a nozzle piece in thenozzle device of a spray coating station.

BACKGROUND OF THE INVENTION

Coating of paper by means of high-pressure coat jets is described inpatent applications PCT/FI96/00525 and PCT/FI96/00526. Conventionally,the nozzle used in spray coating is made from a wear-resistant materialsuch as a ceram or ceram-clad steel, for instance. The function of thenozzle is to atomize the ejected coat jet into an aerosol and then todirect this aerosol to the surface of the web being coated. Hence, thenozzle must be capable of spraying the coat in a homogeneous andall-covering manner in order to achieve a high-quality and homogeneouslayer of the applied coat.

The coat formulation contains a lot of clay or other solids and thepressure levels employed at the nozzle are high. For instance, thesolids may be in the range of about 40-60% and the operating pressure inthe order of 100-200 bar (10-20 MPa). Hence, the wear of the nozzleorifices is rapid and their replacement must be performed at shortintervals notwithstanding the fact that they are made from the mostwear-resistant materials. In the prior art, it has been necessary toreplace the entire nozzle which is a clumsy and time-consumingoperation. Moreover, the replacement has typically been necessary for alarge number of nozzles simultaneously.

For reasons of efficient production, the nozzle parts should bereplaceable without stopping the ongoing coating and affecting the coatquality in a noticeable manner. This need requires that the nozzles mustbe replaceable in small batches, preferably individually. Hence, thereplacement of nozzles could be staggered between the nozzles of thecoating station, thus assuring smooth and uninterrupted coating despitethe nozzle replacements. However, this requirement cannot be fulfilledby conventional techniques or equipment.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a novel type ofnozzle device and method for the replacement of nozzle pieces in modernnozzle assemblies. In this fashion, the above-described drawbacks ofconventional techniques can be overcome.

The goal of the invention is achieved by making the nozzle orifice,which is particularly subject to wear, in a separate, replaceable parthereafter called a nozzle piece. After the nozzle orifice has reached anexcessive degree of wear, the performance of the nozzle can be restoredby replacing merely the nozzle piece instead of dismounting the entirenozzle assembly. Easy replacement of the nozzle pieces is attained bymounting them, e.g., on a band or plate. The nozzle device is providedwith elements serving to retain the nozzle piece in place and elementssealing the nozzle piece against the nozzle device body, the elementshaving a design favouring easy dismounting and remounting. Additionally,the nozzle device is provided with dedicated nozzle piece changeovermeans.

More specifically, the nozzle device according to the inventioncomprises a nozzle device body, replaceable nozzle pieces having nozzleorifices, a clamping means for locking the nozzle pieces to the nozzledevice body, and a nozzle piece replacement apparatus having a pluralityof nozzle pieces, the apparatus being suitable for facilitating rapidreplacement of nozzle pieces. The nozzle device body has a surface whichis adapted to mate under a compressive force with a surface of thenozzle piece. The clamping means has a clamp member adapted to compressthe nozzle piece tightly against the nozzle device body. The clampmember has a surface configured to mate with a surface of the nozzlepiece. The clamping means also has an actuator means adapted to producea force capable of pushing the clamp member toward the nozzle devicebody and also of separating the clamp member and the nozzle device bodyso that the nozzle piece may be replaced.

Furthermore, the method according to the invention for nozzle piecereplacement is characterized by what comprises removing the nozzle piecefrom the nozzle device body by releasing the compressive force exertedby the clamp member so that the mating surfaces of the clamp member andthe nozzle piece move apart, the released nozzle piece is transferredaway from the nozzle device body, a replacement nozzle piece is movedinto position, and the replacement nozzle piece is locked to the nozzledevice body by compressing the nozzle piece against the nozzle devicebody with the clamp member.

The invention offers significant benefits.

The nozzle device according to the invention facilitates rapid andremote-controlled replacement of nozzle orifice. By virtue of equippinga spray coating station with nozzle devices according to the invention,it will be possible to produce a high-quality coat in a continuous runalso when using spray coating techniques. By virtue of utilizing thenovel nozzle devices as disclosed in the method according to theinvention, the nozzles of a spray coating station can be replaced in astaggered manner, whereby the replacement of one nozzle or a few nozzlesat a time does not affect coat quality in coating stations having aplurality of nozzle rows adapted to operate downstream in parallel,whereby the jets of the individual nozzles will partially overlap eachother also in the cross-machine direction.

Other objects and features of the present invention will become apparentfrom the following detailed description considered in conjunction withthe accompanying drawings. It is to be understood, however, that thedrawings are intended solely for purposes of illustration and not as adefinition of the limits of the invention, for which reference should bemade to the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be examined in greater detail bymaking reference to exemplifying embodiments and appended drawings inwhich:

FIG. 1 shows in a partially sectional view a first embodiment of thenozzle device according to the invention for use in the coating of apaper or board web in a spray coating station;

FIG. 2 shows a side view of the nozzle device of FIG. 1;

FIG. 3 shows a second embodiment of the nozzle device according to theinvention for its nozzle piece related parts and in a partiallysectional view; and

FIG. 4 shows schematically a third embodiment of the nozzle deviceaccording to the invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 2, the nozzle device shown therein comprises adevice body 1, nozzle pieces 2 mounted on a nozzle piece carrier band 5,a clamp member 3, a clamp actuator 4 and transfer means 6 of the carrierband 5. The nozzle device is mounted on the spray coating stationstructures via its body 1, however, with the exception of the bandtransfer means 6 which may be mounted on their dedicated transfer meanssupport in the coating station. Reference in the description is made toa nozzle device mounted as in FIGS. 1 and 2 to directions in such adesign. Obviously, the nozzle device can be used mounted at any anglewith regard to the horizontal plane, for instance, so that the jet isdirected straight upright.

The nozzle device body 1 is hollow with a channel and nozzle 7 thereinfor passing the coating into the interior of the nozzle device body andtherefrom further to the nozzle piece 2. The lower part of the body 1includes a sealing seat surface 8, which may be bevelled as shown inFIGS. 1 and 2. To the nozzle device body 1, e.g., to its upper part, isconnected the clamp actuator 4 which at its one end is also connected tothe clamp member 3. The clamp member 3 is shaped so that it has secondsealing seat surfaces 9 with a shape compatible of those of the sealingseat surfaces 8 of the nozzle device body 1 and further is aligned inregard to the nozzle device body 1 so that said sealing seat surfaces 8and 9 will be disposed at a small distance from each other and at leastessentially aligned with respect to each other.

The clamp actuator 4 is arranged to move the clamp member 3 with regardto the nozzle device body 1 so that the distance between the sealingseat surfaces 8 and 9 is adjustable and that a relatively highcompressive force can be exerted thereinbetween.

The nozzle device is provided with transfer means 6 and 6′ of the nozzlecarrier band 5 that via the carrier band 5 are connected to each other.The band transfer means 6 and 6′ are mounted so that the nozzle carrierband 5 can pass from the first transfer means 6 into the gap between thesealing seat surfaces 8 and 9 of the nozzle device body 1 and the clampmember 3 and therefrom further to the second transfer means 6′.Additionally, the edge of the nozzle carrier band 5 may have aparticular perforation helping to control the location of the nozzlepieces and the movement of the nozzle carrier band 5 by means of thetransfer means 6 and 6′.

The nozzle pieces 2 comprise a body part with a nozzle orifice 10 madethereto. At least the rim of the nozzle orifice 10 is made from anextremely wear-resistant material such as a ceram. In the embodimentillustrated in FIGS. 1 and 2, the nozzle pieces 2 are mounted on thenozzle carrier band 5. The nozzle pieces 2 are mounted at a constantspacing from each other and in identical positions with regard to thecrossband direction of the band 5 in order to facilitate accuratepositioning of the nozzle pieces 2 by virtue of the transfer means 6 and6′. The body part of the nozzle pieces 2 is shaped so that, when thenozzle piece is pushed with the help of the clamp member 3 against theseat surface 8 of the nozzle device body 1, the nozzle piece remainscompressed between the seat surfaces 8 and 9 of the nozzle device body 1and the clamp member 3, respectively, whereby it is sealedpressure-tightly against at least one of these seat surfaces. Thus, thenozzle piece will remain tightly sealed seating, e.g., against seatsurface 8 of the nozzle body 1 over the entire rim length of saidsurface 8 on the nozzle device body 1. The corresponding seat surfacesof the nozzle pieces 2 mating with the seat surfaces 8 and 9 are denotedin the diagrams as seat surfaces 18 and 19, respectively.Advantageously, the seat surfaces 8, 9, 18 and 19 are made conical.

In an embodiment of the method according to the invention, thereplacement of the nozzle piece 2 is carried out stepwise in thefollowing sequence:

Coating mix infeed to the nozzle device body 1 is closed by means of adevice-specific check valve (not shown).

Operating the clamp actuator 4, compression at the nozzle piece 2 isreleased and the clamp member 3 is moved in regard to the nozzle devicebody 1 so that the seal surfaces 8 and 9 of the clamp member 3 and thenozzle device body 1, respectively, are moved sufficiently far apartfrom each other, thus facilitating unobstructed transfer of the nozzlepiece 2 off from between said seal surfaces 8 and 9.

The nozzle carrier band 5 is moved by the transfer means 6 and 6′ for adistance equal to that of mutual distance of the nozzle pieces 2 on thecarrier band 5, whereby the worn nozzle piece 2 is moved away frombetween the seat surfaces 8 and 9 and a new nozzle piece 2 is moved intothe gap between said seat surfaces.

With the help of the clamp actuator 4, the clamp member 3 is moved inregard to the nozzle device body 1 in such a direction and with such aforce that the distance between the seal surfaces 8 and 9 of the clampmember 3 and the nozzle device body 1, respectively, are moved closer toeach other, thus causing the new nozzle piece 2 located between saidseal surfaces 8 and 9 to become sealed at least against one of said sealsurfaces 8 or 9.

The device-specific check valve (not shown) is opened, thus facilitatingcoating mix infeed to the nozzle device body 1 and therefrom further viathe nozzle orifice of the nozzle piece 2 in the form of an aerosol sprayto the surface of the web being coated.

In the embodiment shown in FIG. 3, the nozzle pieces 2 are compressed inthe same manner as in the above exemplifying embodiment between thenozzle device body 1 and the clamp member 3. The actuator means requiredto move the clamp member 3 are omitted from the diagram of FIG. 3. Inthis embodiment, the nozzle pieces 2 are unconnected and they have asmooth underside. Mounted close to the nozzle device body 1, the nozzledevice comprises a tubular container 12 into which the nozzle pieces 2can be stacked. Below the tubular container 12 is mounted a supportplate 13 onto which the lowermost one of the stacked nozzle pieces 2 islowered gravitationally or, e.g., by means of a spring (not shown)mounted in the tubular container 12. With regard to the device 1 and theclamp member 3, the support plate 13 is positioned at a height that,when the gap between the clamp member 3 and the nozzle device body 1 isopened into the replacement position of the nozzle piece 2, allows anunobstructed passage of the lowermost nozzle piece 2 from the stack toreplace the worn nozzle piece 2 from under the nozzle device body 1.From the stack, the lowermost nozzle piece 2 is pushed into the positionunder the nozzle device body 1 by means of a pusher rod 11 adapted tomove immediately above the upper surface of the support plate 13. Inthis manner, the worn nozzle piece 2 will be displaced aside pushed bythe replacing nozzle piece 2.

In FIG. 4 is shown an embodiment, in which the nozzle pieces 2 areunconnected and the unused nozzle pieces 2 are stacked in a tubularcontainer 12. Between the tubular container 12 and the nozzle device 17is adapted a rotatory disc 14 having six holes suited to support thenozzle pieces 2. In this embodiment, the replacement of the nozzlepieces 2 is carried out so that, as soon as the nozzle device 17 hasreleased the worn nozzle piece 2, the disc 14 is rotated 60°, wherebythe next nozzle piece 2 will be aligned with the sealing seat surfacesof the nozzle device body. Simultaneously, a new nozzle piece 2 will belowered into the empty hole introduced by the rotating disc 14 under theexit end of the tubular container 12 and the worn nozzle piece isremoved by means of a nozzle piece collection mechanism (not shown). Thelocked sealing of the nozzle piece 2 against the nozzle device body 1and unlocking thereof, respectively, are arranged in a similar manner asdescribed above. Also an embodiment adapted to use the disc 14 as theclamp member 3 (cf. FIGS. 1 and 2) is feasible.

In addition to those described above, alternative embodiments of thepresent invention may be contemplated.

An embodiment having the nozzle pieces arranged on a carrier band isshown in FIG. 1. Differently from this, the nozzle carrier band 5 withthe separate nozzle pieces 2 being carried on the band may be replacedby a single rigid carrier body with the nozzle pieces 2 integratedthereon. Also along the length of such a rigid carrier body 5, thenozzle orifices are most advantageously located at a constant spacingfrom each other. The nozzle piece carrier body 5 may also have its edgesprovided with perforation or holes helping to control the location ofthe nozzle orifices and the movement of the nozzle carrier body 5 bymeans of gears, for instance.

An embodiment having the nozzle pieces 2 handled as separate pieces andthe new nozzle pieces 2 arranged into a stack is shown in FIG. 3. Thetransfer of these nozzle pieces 2 in FIG. 3 is shown implemented using apusher rod 11. Differently from this, the transfer of the nozzle piecesmay be arranged to occur by means of, e.g., a band adapted to run underthe tubular container 12 and the nozzle device body 1 and,simultaneously, above the mating surface of the clamp member 3.

Now referring to the embodiment shown in FIG. 4, an alternativepossibility is to manufacture the nozzle pieces 2 as integral elementsof the discs 14. In this type of embodiment, the entire disc 14 may bereplaced by a new disc 14 after all the nozzle pieces 2 of the firstdisc 14 are worn out. Thence, the tubular container 12 would beredundant.

Thus, while there have been shown and described and pointed outfundamental novel features of the present invention as applied topreferred embodiments thereof, it will be understood that variousomissions and substitutions and changes in the form and details of thedevices illustrated, and in their operation, may be made by thoseskilled in the art without departing from the spirit of the presentinvention. For example, it is expressly intended that all combinationsof those elements and/or method steps which perform substantially thesame function in substantially the same way to achieve the same resultsare within the scope of the invention. Substitutions of elements fromone described embodiment to another are also fully intended andcontemplated. It is also to be understood that the drawings are notnecessarily drawn to scale but that they are merely conceptual innature. It is the intention, therefore, to be limited only as indicatedby the scope of the claims appended hereto.

What is claimed is:
 1. A nozzle device for use in a spray coatingstation for coating a paper or board web, comprising: a nozzle devicebody; a nozzle piece having a nozzle orifice, wherein said nozzle devicebody and said nozzle piece each have a surface adapted to mate togetherunder a compressive force; a nozzle piece replacement apparatus suitablefor holding a plurality of said nozzle pieces, and for facilitatingrapid replacement of nozzle pieces on said nozzle device body; and aclamping means for removably locking said nozzle piece tightly to saidnozzle device body, said clamping means comprising; a clamp memberhaving a surface configured to mate with said nozzle piece; and anactuator means suitable for exerting a force to push said clamp memberso that said nozzle piece becomes tightly and removably locked to saidnozzle device body when the actuator means exerts the force and suitablefor moving said clamp member so that said nozzle piece may be removedfrom said nozzle device body by said nozzle piece replacement apparatuswhen the actuator means does not exert the force.
 2. The nozzle deviceof claim 1, wherein said nozzle piece replacement apparatus comprises acarrier band to which a plurality of said nozzle pieces are mounted, anda moving means for moving said carrier band.
 3. The nozzle device ofclaim 1, wherein said nozzle piece replacement apparatus comprises atubular container suitable for stacking a plurality of said nozzlepieces, and a transfer means for transferring stacked nozzle pieces, oneat a time, to said clamping means.
 4. The nozzle device of claim 3,wherein said nozzle piece replacement apparatus comprises a disc.
 5. Thenozzle device of claim 3, wherein said nozzle piece replacementapparatus comprises a band.
 6. The nozzle device of claim 3, whereintransfer means comprises a pusher rod.
 7. The nozzle device of claim 1,wherein said nozzle piece replacement apparatus comprises a disc.
 8. Thenozzle device of claim 1, wherein said nozzle piece replacementapparatus comprises a band.
 9. The nozzle device of claim 1, whereinsaid nozzle piece replacement apparatus comprises a pusher rod.
 10. Thenozzle device of claim 1, wherein said nozzle piece replacementapparatus comprises a disc to which a plurality of said nozzle piecesare mounted, and a means for rotating said disc.
 11. The nozzle deviceof claim 1, wherein said mating surfaces of said nozzle device body andsaid nozzle piece are shaped substantially as a truncated cone.
 12. Thenozzle device of claim 1, wherein said mating surfaces of said nozzlepiece and said clamp member are shaped substantially as a truncatedcone.
 13. A method for replacing a nozzle piece of a nozzle device usedin a spray coating station for coating a paper or board web, comprising:removing the nozzle piece from a body of the nozzle device, wherein thenozzle piece is tightly and removably locked to the nozzle device bodyby a clamping means comprising a clamp member having a surfaceconfigured to mate with the nozzle piece, and an actuator means suitablefor exerting a force to push the clamp member so that said nozzle piecebecomes tightly and removably locked to said nozzle device body when theactuator means exerts the force and suitable for moving said clampmember so that said nozzle piece may be removed from said nozzle devicebody when the actuator means does not exert the force, wherein thenozzle piece is removed by releasing the force applied by the actuatormeans to form a gap between the nozzle piece and the clamp member,wherein removing the nozzle piece is accomplished by releasing the forceexerted by the actuator means; transferring the released nozzle pieceaway from the gap; transferring a replacement nozzle piece into the gap;and causing the actuator means to exert the force so as to removablylock the replacement nozzle piece between the clamp member and thenozzle device body.